The coupling of the efflux of sodium ions to the protonmotive force generated by the action of light on membrane bound bacteriorhodopsin in membrane vesicles of Halobacterium halobium has previously been established by this laboratory. The mechanism of the H ion/Na exchange will be investigated further with particular emphasis on the nature of the carrier(s) involved. On the assumption that these carriers are proteins which will bind the ions involved, an attempt will be made to isolate these binding proteins and to reconstitute them in an artificial lipoprotein vesicle so that their mechanism of exchange may be studied in more detail. The coupling of the uptake of amino acids to the uptake of sodium will be studied from the standpoint of stoichiometry and mechanism. An attempt will be made to isolate and reconstitute into liposomes, amino acid carriers which require the cotransport of sodium for uptake to occur. The cotransport of glutamate with sodium in E. coli will be studied by attempting to isolate and characterize mutants with defects in this mechanism of amino acid transport. BIBLIOGRAPHIC REFERENCES: MacDonald, R.E., Greene, R.V. and Lanyi, J.K. 1977. The light-activated amino acid transport system in Halobacterium halobium vesicles. Role of chemical and electrical gradients. Biochemistry 17. In press. MacDonald, R.E., Lanyi, J.K., and Greene, R.V. 1977. Sodium stimulated glutamate uptake in membrane vesicles of Escherichia coli. Role of ion gradients. Proc. Natl. Acad. Sci. U.S. 74. In press.